Laboratory studies of foam separation were conducted to determine the feasibility of this process for reducing B.O.D., solids content, and foaming tendency of clarified kraft mill effluent. Since kraft pulping wastes have a natural tendency to foam, it was expected that the foaming process, which has been found to be useful in treating domestic wastes, might have applications in treatment of these effluents. Both continuous flow and batch experiments were conducted, and liquid and foam heights, liquid feed rates, air sparging rates, and temperature were varied over wide ranges. The B.O.D. reduction in the treated liquid was disappointingly small, averaging less than 5 per cent, and the B.O.D. enrichment in the foam phase was in most cases less than 1.5 times that of the feed. Foaming tendency, however, was significantly reduced by the intentional foaming process. The experimental results suggest that the reductions in B.O.D. and foaming tendency were related to the separation of the tall oil components of the waste. Apparently the remaining B.O.D.- producing materials were not surface active and did not attach themselves to the surface-active components. The cost of using a foam process on kraft mill wastes is estimated to be four to five cents per 1000 gallons of feed; this cost is exclusive of further processing of the concentrated foamate. Based on control of foaming tendency alone, the process would be unattractive from a cost standpoint. (Author)

Program no. 12040 EUG, grant no. WPRD 117-01-68. Includes bibliographical references (pages 49-50). Microfiche.